On the Estimation of the Noise Emitted by the Vibration of a Circular Plate

Machine noise is composed of air-borne noise, which is strictly of aerodynamic nature and which originates from openings like air-intake and exhaust, and of the noise emitted by the vibration of machine surface. The surface vibration noise caused by exciting forces depends on the transmitting or impeding characteristics of the machine structure and on the vibration characteristics of the external surface. Namely, surface vibration noise is influenced by three factors : exciting forces, mechanical transmission impedance and radiation factors. The radiation factor depends on the ratio between air-borne noise power and vibration power of the structure on its surface. Clearly, improvements in one of these three factors can lead to a reduction in overall noise. In this paper, the relation between the vibration of a circular plate clamped at the edge and the noise originated by the surface vibration are studied, and some interesting results are obtained in connection with a method to estimate the sound pressure level and the frequency characteristics of the noise by the measurement of the vibration.